This application claims the priority of German Patent Document No. 10037807.2, filed Aug. 3, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a brake block for a brake braking an open-end spinning rotor, comprising a take-up for releasable affixing to a brake block support, also comprising at least a first braking surface and a second braking surface.
Brake blocks for brakes for open-end spinning rotors have the disadvantage that they have to be exchanged before they have reached the maximum permissible amount of wear, because the brake effect is no longer sufficient due to a smoothing of the surface. For this reason, it is known in the prior art (German published patent application 196 18 261), to provide brake blocks with two applicable sides. This means that the brake block does not immediately become unusable due to wear, but rather that, after the brake block supporter is released, the brake block is simply turned around and can be re-used by applying its second braking surface after it has been re-affixed to the brake block supporter. The material of the brake block is thus better utilized. The disadvantage remains, however, in that the brake blocks must be turned around at all spinning stations of an open-end spinning machine, which is extremely time-consuming.
It is an object of the present invention to design a brake block of the above mentioned type in such a way that an intermediary turning around in order to increase the life of the brake block becomes superfluous.
This object has been achieved in accordance with the present invention in that, the first braking surface and the second braking surface face in the same direction, the second braking surface is set back a certain distance in comparison to the first braking surface, so that the second braking surface comes into contact with the open-end spinning rotor only after wear of the first braking surface.
In preferred embodiments, the first braking surface is effective directly after the first assembly until it reaches a certain degree of wear. Hereafter, the second braking surface comes into effect, in addition to the first, braking surface. As the second braking surface is still unused, it can be assumed that there is an improvement in brake action in the sum of the braking effect of the first and the second braking surface even in the second life span of the brake block.
Theoretically, more than two different braking surfaces can be realised. The number of possible braking surfaces is determined by the permissible surface pressure of each braking surface. It is in any case possible, due to the features of the present invention, to at least partly compensate for the reduced friction coefficient of the first braking surface by means of the second braking surface which is then supported on the open-end spinning rotor, hereby increasing the life of the brake block.
In certain preferred embodiment of the invention, the first braking surface and/or the second braking surface can consist of section surfaces at a distance from one another. It is for example possible that the first braking surface consists of two section surfaces, between which the second braking surface is arranged. Thus the symmetry is ensured for the entire lifetime of the brake block. To this end, the two section surfaces of the first braking surface are together approximately the same length as the second braking surface. Favorable values have been achieved for open-end spinning rotors when the entire length of the two section surfaces of the first braking surface and the length of the second braking surface are each approximately the same and measure approximately 15 to 20 mm in length.
It has been established as advantageous when the amount by which the second braking surface is set back in relation to the first braking surface corresponds to approximately half the lifetime of the brake block. For example, the amount by which the second braking surface is set back can measure between 0.4 mm and 0.8 mm.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings.